Cass Mann is one of the world's longest-term HIV-positive diagnosed gay men, now in his third decade of living with HIV, and the founder of UK's only gay men's HIV/AIDS charity Positively Healthy, which provides HIV services including education, support, and peer counselling. Here he talks about how back rooms and dark rooms contribute to the spread of HIV. Back rooms and dark rooms are stand-alone clubs or rooms attached to bars or pubs that have no lighting and where people have anonymous sex with people they can't even see in the dark. When you can't see your partner, you can't make any judgments about your potential partner. You can't tell if they appear healthy or are obviously ill. You can't make an informed choice. Back rooms and dark rooms may be a major venue for HIV transmission today. For more information, visit http://www.posh-uk.org.uk/ and http://www.AIDSvideos.org/.